yeah since my last post on the discussions page I've continued playing Falco
I'll probably go with Falco but I want to see other recommendations just in case
Honestly, Falco or Marth would fit the best with Sheik just barely working for perfect matchup coverage while still using Jigglypuff. Fox would work, but people have a tendency to play only Fox once they pick up Fox, and the ones that dual-main Fox haven't used in the past and still don't use Jigglypuff (nor Falcon, but still). I don't know, maybe you would be the first Fox Puff dual-main, and if so go for it! Otherwise, aside from the previously mentioned, Peach hates Puff to the point that she doesn't work with her. Lol, no, but Peach Puff generally doesn't work, and Falcon doesn't really complement Jigglypuff in this current metagame. Puff only is difficult to practice (just see only Hungrybox doing that at top level). However, really you should use who you like as well, and if you like the spacies and would like to use one of them as a Puff Spacie dual-main, go for it.
So yeah, for your case, probably Falco, although you would be one of the unique dual-mains of using Fox Puff or Falco Puff either way.